Influence of mixing section inlet and diffuser outlet velocities on the performance of ejector-expansion refrigeration system using zeotropic mixture

It is known that the performance of vapor compression cooling systems can be increased thanks to the ejector. In the literature, there are many studies on the subject, in which mathematical models of ejector-expansion cooling systems are developed. However, the refrigerant velocities at the mixing section inlet for the secondary flow (suction stream) and diffuser outlet were neglected in these studies. In the mathematical model used in this study, the velocities in both sections are considered and the system performance is calculated. The performance assessment of an ejector-expansion refrigeration system was realized in the case of using the R600a/R290 refrigerant mixture as a working fluid. Thus, the effect of zeotropic refrigerant mixtures on the system performance is also investigated, considering the refrigerant velocities at the mixing section inlet and diffuser outlet. According to the obtained results, it has been found that the cooling performance of the system that uses R600a/ R290 mixture as a refrigerant is 5.8%-7% higher when the velocities at the mixing section inlet and diffuser outlet are considered compared to the neglected one. The exergy efficiency is also calculated to be around 4.6% lower when the ejector mixing section inlet and diffuser outlet velocities are neglected.

Automated summary

The performance of vapor compression cooling systems can be increased thanks to the ejector, but the impact of refrigerant velocities has been neglected in some previous studies. By considering velocities, the study calculated the performance of a system using R600a/R290 refrigerant mixture, finding higher cooling performance and lower exergy efficiency when velocities are taken into account.